Automatic fire alarms



Nov. l, 1955 E wlNFiELD 2,722,582

AUTOMATIC FIRE ALARMS Filed June 25, 195'1 l Z y lima/6 /B United States Patent() AUTOMATIC FIRE ALARMS Edwin Winfield, Willowdale, Ontario, Canada Application June 23, 1951, Serial No. 233,137

14 Claims. (Cl. 20G-138) My invention relates toimprovements in fire alarms of the automatic type in which a thermally actuated switch is employed to close an electric circuit.

A major object of the invention is to provide a fire detecting apparatus by which an alarm may be signalled as fast as possible at the outbreak of a fire and which is devised so as to keep clear of signalling false alarms.

My present invention is an improvement on the automatic fire alarm disclosed in my Patent No. 2,247,539; and the improved lire alarm structure is illustrated in the accompanying drawing in which Fig. l is an elevational view of a fire alarm device constructed in accordance with the present invention and showing the mercury switch at about the pitch it would assume at normal temperature,

Fig. 2 is a vertical sectional view taken on line 2-2 of Fig. 1,

Fig. 3 is a similar View to Fig. 1 but showing the mercury tube at a steeper pitch such as it would assume at a low temperature, and

Fig. 4 is a detail of a variant form of the invention, and Fig. 5 is a section on line 5 5 of Fig. 3.

ln the drawing, A and B are heat responsive coils of bimetallic material and they are similar to each other. Coil A is fully exposed to the ambient atmosphere. Coil B is contained in an apertured housing R of a suitable type for bringing about a delay or lag in transfer of heat upon outbreak of a fire. The housing has an opening R which provides for exchange of heat and for the arm D of coil B to extend freely for up and down movements. The arm of coil A is denoted at C. The coil-arms move upwardly with increase in temperature. The outer end E of the arm C is provided with a swivelly attached hanger U, the lower end of which is swivelly attached to an end of the mercury tube G by means of the clip V. Similarly, the outer end F of the other arm D is provided with a swivelly attached hanger X, the lower end of which is swivelly attached to the other end of the tube G by means of the clip Y. A weighting ring encircles the tube between said clips as a stabilizing agent, as indicated at Z. The lead wires S and T, which extend from the tube, are attached to the binding posts on the panel 11. The mercury switch controls the circuit 12 to an annunciator, such as the siren 13 which is energized by a storage battery or batteries, indicated at 14.

The structure above described is substantially the same as that disclosed in Patent No. 2,247,539 above referred to. The arrangement is such that upon outbreak of fire the coil A is affected by heat faster than coil B with the consequence that the pitch of the tube is reversed and an alarm is given when the switch is closed. Minor increases in temperature do not produce an alarm.

While the fire alarm device disclosed in said Patent No. 2,247,539 affords a very fastinstrument for use in buildings which are not heated artificially, it does not provide one which I consider sufiiciently fast for use in artificially heated buildings. In a building which is not heated artificially the mercury tube of the fire alarm may ice be assigned a slope downward to the left corresponding to a temperature differential of say 20 F. i. e., the mercury tube would level up if temperature increased by 20' F. at coil A without any increase at coil B. In this way, a quick alarm would be furnished with complete freedom from false alarms. Artificially heated buildings arehowever permitted on occasions to cool to quite a low room temperature and then are heated up quickly. It has been found that under these conditions, and with adequate housing for coil B, false alarms can be experienced even when the mercury tube is given a pitch downward to the left corresponding to a considerably greater temperature differential than 20 F.

My patented fire alarm above referred to is entirely satisfactory for use in buildings which are not heated artificially. The improved fire alarm of the present invention provides a much faster and satisfactory instrument for use in a building which is heated artificially. The improvement comprises the leaf spring H located subjacent the coil B and curved upwardly from the inner side of the lower housing wall to which it is secured by screws P or the like. The free end of the spring H is disposed beneath the arm D and is in contact therewith only at and below a predetermined specified temperature.` The spring acts on the arm D when this arm moves downwardly incidental to a drop in temperature.

Whereas the structure described in Patent No. 2,247,539 provides for the alarm being secured in identical time interval following fire outbreak, regardless of the ambient temperature at the instant of fire outbreak, the incorporating of spring H in the structure provides, below a specified temperature point, for a variation in the time required to secure a signalling alarm, accordingv to temperature in the immediate vicinity of the device at the moment of fire outbreak, with the time interval increased as temperature at instant of fire outbreak is lowered. Above the specified temperature point the spring H is inoperative and therefore the instrument functions the same as the fire alarm of my patent heretofore men tioned.

My improved structure including the spring H is specifically designed for operation in heated buildings such as those used for dwellings and is devised' on the basis that in the lar-ge majority of fires the room temperature of the heated building at the instant of fire outbreak is in or near the range of 60 to 80 F.

lt is rare that a fire occurs in a heated building when the temperature therein is down to or below freezing point.

It is not objectionable to have a lire detecting device which is relatively slow and inefficient if the temperature is low at the instant ofkfire outbreak provided that the instrument functions quickly and efficiently when the ambient temperature is at a normal range at the instant of fire outbreak. Spring H brings about this desirable accomplishment and protects against the signalling of false alarms.

From tests made on a fire alarm constructed in accordance with this invention the following figures are given. With an ambient temperature of 90 F. and with a setting such that the free end of spring H is just touching the lower side of arm D of coil B the tube switch has a down.- ward pitch to the left corresponding to a temperature differential of 20 F. If the ambient temperature is decreased to F. and remains thereat the end E of coil-arm C descends freely but the end F of coil-arm D is slightly arrested or retarded in its descent due to upward pressure of spring H thereon. As a result the pitch.

of the tube `switch is increased slightly and corresponds. to a temperature differential of between 21 and 22Y With a drop in temperature from 80 F. to 70 F. the upward pressure of the distal end of spring H on the coilarm D is increased moderately and there is only a slight further lowering of coil-arm D while the temperature is decreasing to the 70 point. At a temperature of 70 F. the pitch of the mercury tube corresponds to a temperature differential of nearly F.

With a continued drop in temperature the spring H is caused to exert an intensified pressure in upward direction on the coil-arm D and thus the descent of the coilarm D is further retarded or arrested, whereas the coilarm C continues to descend freely. With a drop in temperature to zero the pitch of the mercury tube corresponds to a temperature differential of F.

In this way false alarms incidental to a rapid reheating of the building are adequately guarded against. Due to the acute pitch assumed by the tube at zero temperature a sudden increase in temperature to about 50 F. would have to take place before the tube would level up.

Although the invention provides a re alarm which is relatively slow and inefficient for sounding a warning of re outbreak when the temperature is around or below freezing point, it is on the other hand fast and efficient when the temperature is at a normal range in the order of say to 80 F. Accordingly it will be understood that the device obviates false alarms. Moreover it has the virtue of speed and efficiency in detecting fires in artificially heated buildings.

A distinctive feature of the present structure resides in spring H which is highly efficient and capable of producing quick action with temperature change. The likelihood of false alarms is far greater with lower temperature because the colder it is within an artificially heated building the greater is the opportunity for a rapid and continued temperature upsurge. Spring H increases the temperature differential in proportion to the decrease in temperature. The spring operates to prevent false alarms by supplying a controlling force only to the extent necessary for keeping the mercury tube at a pitch consistent with prevailing temperature for obviating false alarms.

Referring back to the test made, it will be noted that a stop J is provided below the arm D. This is located at a point to prohibit further downward movement of the arm D when temperature drops below zero. Further downward movement of arm C is prohibited by a stop K.

In the arrangement of the device as set forth the arm D of coil B moves upwardly away from the spring l-l when the temperature rises above F. The spring is relaxed by disengagement of the arm D. When the temperature rises above 90 F. the device operates in a manner similar to the device of Patent No. 2,247,539.

When the temperature is elevated and on the increase, the arm D of coil B is stopped by the stop L at about F. The arm C of coil A continues to move upwardly with increase in temperature and is stopped at about F. after a reversal of the mercury tube is brought about and an alarm is sounded due to the closing of the switch. ln this way an alarm is ultimately secured in the rare event of a fire breaking out which does not increase the ambient temperature with sufficient rapidity to cause an alarm by differential movement of the arms C and D before the stops L and M are encountered.

The invention as above described may be modified to enable a lighter and more sensitive spring H to be employed in order to hasten the securing of an alarm following an outbreak of re. In the use of a lighter or more sensitive spring a somewhat greater length of bimetal may be used in coil A than in coil B. The effect of this is that, for each change in temperature (decrease or increase) the end E of coil-arm A moves a slightly greater distance than the end F of coil-arm D. Therefore when temperature is falling the end F of arm D does not move downwardly as far as the end E of arm C for each temperature drop. As a result the upward pressure of the free end of spring H against the arm D is not required to be of sufcient strength to bring about a gradually increasing differential movement to enhance the pitch of the mercury tube downwardly to the left and away from the contacts therein. Spring H need only be of a strength to assist in bringing about said differential movement of said arms. The lighter and more sensitive spring H is less expensive to manufacture.

An advantageous feature of the variant form of the device in which the coil A has a greater length of bimetal is that the end E of the arm C of this coil is adapted to travel upwardly through a greater distance than the end F of coil-arm D as the temperature progressively increases. With the device assigned a standard temperature differential at 90 F. it will be understood that, with coil disparityl present, less time will elapse from the instant the temperature passes 90 F. in its upward course to the instant of the reversal of the mercury tube than would be the case were the coils made similar in bimetal characteristics. Consequently an alarm is more quickly secured.

lf desired, and when employing either similar or dissimilar coils A and B, the spring H is in the form of a member made of heat-responsive bimetal, and arranged so that the free end moves upward as temperature falls. intensification of pressure against the underside of arm D of coil B, as temperature falls, is thus secured by two factors, viz., the downward movement of arm D and the upward movement of the free end of member H. This modified form of the invention is illustrated in Fig. 4. The bimetallic member which is employed to act on the arm D of coil B in lieu of the spring H is designated at Q.

From the preceding description it will be manifest that my invention as herein set forth produces a highly desirable and efficient re alarm which is particularly adapted for installation in artificially heated buildings.

What l claim is:

l. A thermostat quick change temperature detector for operating alarms comprising in combination a mercury tube having contacts sealed therein and a globule of mercury displaceable for closing said contacts, heat responsive agents jointly controlling the operation of said tube by a differential of temperature reaction, and flexible means arranged to apply a damping action on one of the heat responsive agents to increase the tilt of the tube away from the closed position of said contacts so as to avoid a false alarm in reverse movement of the tube.

2. A thermostat quick change temperature detector for operating alarms comprising in combination a mercury tube having contacts sealed therein and a globule of mercury displaceable for closing said contacts, heat responsive agents jointly controlling the operation of said tube by a differential of temperature reaction, and a resilient device arranged to apply damping action on one of the heat responsive agents to increase the tilt of the tube away from the closed position of said contacts whereby to avoid a false alarm in reverse movement of the tube.

3. A thermostat Iquick change temperature detector for operating alarms comprising in combination a mercury tube having contacts sealed therein and a globule ot mercury displaceable for closing said contacts, heat responsive agents jointly controlling the operation of said tube by a differential of temperature reaction, said heat responsive agents having arms on which the tube is suspended, and a spring arranged to bear on an arm of one of the heat responsive agents to increase the tilt of the tube away from the closed position of said contacts whereby to avoid a false alarm in reverse movement of the tube.

4. A thermostat quick change temperature detector for operating alarms comprising in combination a mercury tube having contacts sealed therein and a globule of mercury displaceable for closing said contacts, heat responsive agents jointly controlling the operation of said tube by a differential of temperature reaction. said heat responsive agents having arms on which the tube is suspended, and a heat responsive agent in the form of a metal bar supported to press on the arm of one of the coils to increase tilting movement of the tube away from the closed position of said contacts.

5. A thermostat quick change temperature detector for operating alarms comprising in combination a mercury tube having contacts sealed therein and a globule of mercury displaceable for closing said contacts, heat responsive agents jointly controlling the operation of said tube by a differential of temperature reaction, said heat responsive agents being in the form of coils of bimetal,- lic material having supported inner ends and free outer ends providing arms, whose ends are disposed in 'uxtaposition, hangers depending from the ends of said arms, a mercury contactor tube jointly supported by said hangers for tilting movement, and a heat responsive agent in the form of a bimetallic bar supported at an end below one of said arms and disposed to move upwardly to retard downward movement thereof with decrease in ambient temperature.

6. A device as set forth in claim 5, in which means are provided for causing a differential of temperature reaction between said heat responsive agents.

7. A thermostat quick change temperature detector for operating alarms, comprising in combination a support provided with a housing having an opening for admitting heat to the interior thereof such that an abrupt change in temperature is communicated to the interior in retarded manner to bring about a differential of temperature between that within the housing and that of the exterior atmosphere, a pair of heat responsive agents operably mounted on said support, one of which is located within said housing and the other of which is disposed outside of the housing so as to be freely exposed to the ambient atmosphere, a mercury contactor tube, means by which said mercury contactor tube is jointly suspended from said heat responsive agents for tilting movement, and yieldable means for applying damping pressure on the heat responsive agent within the housing to increase the pitch of the tube when the tube is tilted downwardly of the contact end whereby to obviate a false alarm when the temperature of the ambient atmosphere increases.

8. A structure as dened in claim 7, in which the heat responsive agents are coils of bimetal havingarms, the arm belonging to the coil in the housing extending freely through a lateral opening in the housing, and in which the suspension means for the mercury contactor tube comprises hangers pivotally depending from said arms and swivelly attached to the end portions of the tube.

9. A structure as defined in claim 7, and in which the heat responsive agents are coils of bimetal constructed to have a dilerential of temperature reaction.

10. A structure as deiined in claim 7, in which the heat responsive agent in the housing is a coil of bimetal having an arm, and in which the movable means for applying pressure on the heat responsive agent comprises a spring supported and arranged to retard said arm against downward movement due to decreasing temperature within the housing.

11. A structure as defined in claim 7, in which the heat responsive agents are coils of bimetal having arms laterally extended and supporting the mercury contactor tube, and in which the means for applying pressure on the heat responsive agent within said housing comprises a leaf spring supported at an end in the housing below the arm of the heat responsive agent therein and having a normally relaxed free end disposed to be engaged by the arm belonging to the heat responsive agent in said housing whereby to retard downward movement of this arm.

12. A thermostat quick change temperature detector for operating alarms, comprising in combination a mercury tube having contacts at an end thereof and a globule of mercury displaceable for closing said contacts, a pair of heat responsive agents mounted to jointly suspend said mercury tube, one of said heat responsive agents comprising a first bimetallic coil having an arm connected by a hanger to the contact end of said mercury tube, the other heat responsive agent comprising a second bimetallic coil connected by a hanger to the other end of said mercury tube, said heat responsive agents suspending said mercury tube at a tilt sufcient to displace the globule of mercury away from said contacts and being capable of raising said mercury tube with increase of ambient temperature and lowering it with decrease in ambient temperature, a housing enclosing said rst bimetallic coil and provided with an opening for admitting heat to the interior thereof in retarded manner to bring about a differential of temperature between that within the housing and that of the exterior atmosphere, and yieldable means disposed to apply a damping action on the arm of said rst coil to increase the tilt of said mercury tube as it is lowered by said heat responsive agents with decrease in ambient temperature.

13. An apparatus as set forth in claim 12, in which a limiting stop is provided below the arm of said first coil, and in which said yieldable means applies said damping action as this arm moves toward said limiting stop.

14. An apparatus as set forth in claim 12, and in which the yieldable means is of a resilient character and assists in a reverse movement of the arm of said first coil in which the mercury tube is raised with temperature increase.

References Cited in the file of this patent UNITED STATES PATENTS 674,867 Howe May 28, 1901 1,478,084 Whittington Dec. 18, 1923 1,881,919 Patton Oct. 1l, 1932 2,247,539 Winfield July l, 1941 2,518,503 Sparklin Aug. 1S, 1950 

